1. Field of Invention
The present invention relates to a measuring device, especially to a surface tension measuring device and a method thereof.
2. Description of Related Art
Surface tension is caused by cohesion of material molecules. Several effects of surface tension can be seen in our daily lives. For example, rise or fall of liquid in a capillary tube, beading of water, and a fountain pen in which surface tension keeps the ink on a nib and not dropped due to gravity. There is also a plurality of applications of surface tension effect in industrial techniques such as fluid seal, spin coating, printer ink jetting, surface wetting, etc.
The surface tension effects and applications are pervasive in many areas so that the surface tension measurement plays an important role on industrial and research institutes. Most of surface tension measuring techniques available now use contact angle measuring instruments. The instrument includes a machine, a prime lens, a camera, a back light module, a computer and algorithm package software. The measured value of the contact angle, estimated value of gas-liquid surface tension and calculated value of gas-solid surface tension are substituted into a force balance equation of the droplet interface so as to determine solid-liquid surface tension (or abbreviated as surface tension). However, such measuring method has disadvantages of long measuring time, large space occupation, high instrument cost and high operation complexity.
Refer to Taiwanese Pat. No. 200928343, a surface tension measuring technique is revealed. A container with a liquid analyte and a vertical tube are connected by U-shaped tube sets. An outlet of the vertical tube is located at the same level of the container. Then fill a liquid analyte into the container. When a hemispherical drop is formed on the outlet of the vertical tube, measure the level difference between the liquid level in the container and the liquid level in the vertical tube. In case the effect of gravity on the drop shape is negligible, the measured results obtained are substituted into an equation derived from the force balance relations so as to get the surface tension of the liquid analyte. However, there are a plurality of factors that affect the precision of measurement such as the tube length, the location of the tube (outlet), and the effect of gravity on the drop. Thus the measurement errors increase, combined with other disadvantages such as large space occupied, high instrument cost and high operation complexity.
Like many other common physical phenomena, how surface tension occurs and the measurement of surface tension play important roles in the scientific education. Yet most of surface tension measuring instruments available now are with defects of high cost, inconvenience in carrying and considerable complexity in measuring and they are unable to be applied in our daily lives or teaching.
Thus there is a need to provide a surface tension measuring instrument and a method thereof that reduce the measuring time, the space occupied, the equipment cost, the operation complexity and overcomes the above shortcomings.